99 blazer, auto climate control inop and service 4x4 light on- checked powers and grounds to climate control, all good- checked power and ground to control for blower- all good- 5v on pcm monitor wire- ordered control- found connector at 4x4 switch had bad connection, under further inspection found switch at fault- switch arrived first so installed- 4x4 completely inop, climate control operates normally- reconnected old switch to verify, still inop- after sever cycles of the key, 4x4 works and climate control inop- rechecked all powers and grounds- wiggled harness to try to duplicate short- checked common gounds- unable to pinpoint cuse of issue- has anybody seen anything like this before? any help would be appreciated
thanks- jason

 

Both of these devices communicate on the data link buss to the other systems in the truck. It sounds like there may be a faulty connection somewhere in the buss that is causing the intermittent concerns. The data lines for both of these devices run to SP201 (splice pack) which is located above the accelerator/brake pedals. It will be a bunch of wires running into a black connector with nothing out the other side. I would check there first.